Neural Circuits:
Wiring and
Tuning
Navee%Kaur%
Friday,%September%29,%2017%
Synaptic Tuning
Three specific concepts associated with synaptic tuning:
v Long-Term Potentiation (LTP)
v Long-Term Depression (LTD)
v Spike-Timing Dependent Plasticity (STP)
Source
LTP:
v High-frequency presynaptic stimulation, or
v Low-frequency stimulation with postsynaptic depolarisation.
LTD:
v Low frequency stimulation
v Decrease in synaptic efficacy.
Significance
Definition
of STDP
Hardware Implementation of
STDP Example
Neurons that fire together
wire together.”
v Hebbs Law
Synaptic Wiring
v Topographic Maps
Map Development
Mechanisms
v Chemospecific matching:
Similarity between input
neurons (or output) is
encoded by similarities
expressed with a molecular
gradient.
v Based off of Sperrys
Chemoaffinity Hypothesis
Map Development Mechanisms
vActivity-dependent matching:
Similarity is encoded by correlations in activity
Ø Coactive = more similar
How Does This Information
Affect Our Model?
v Our model:
Activity-dependent
Focuses on one
neuron at a time.
Short vs. Long-Distance
Guidance
Long-Distance:
v Chemotaxis mechanisms
v Structural type mechanisms
Short-Distance:
v Similar to our model
Conclusion
v How do we fine tune the strength of our current model?
1. Axonal Guidance
2. Strengthening/weakening of individual synapses based on relative
timing of pre/postsynaptic timing.